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INFO GLOSSARY

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


AGC
Automatic Gain Control: automatically adapting the sensitivity of the sensor to the overall brightness of the image scene.

Aperture
The aperture of an optical system (lens) is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane.

API
Application Programming Interface.

Aspherical
An aspherical lens is a lens, usually glass, which is used on a camcorder or SLR camera. Aspherical lenses are typically lighter weight than traditional lenses and do not conform to the typical sphere shape of lenses, meaning that their profile does not contain a sphere or any part of a sphere. Aspherical lenses are used to reduce certain types of aberration typically showing a much clearer picture than their traditional lens counterparts.

Backlight
A light source which illuminates the object from the bottom side. Advantage of backlight can be found on a higher contrast of the the object edges.

Bayer-filter
Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image.The filter pattern is 50% green, 25% red and 25% blue

Blooming
“When light passes the lens of a digital camera and is captured by the CCD it is converted into an electrical charge. There is a limit to how much charge each pixel or photosite can store. If there is too much charge for one photosite it will overflow to its neighbouring pixel causing an effect which is called blooming or streaking”.

CCD
Charge Coupled Device - a light sensitive chip used to record the image.

CCTV
Closed Circuit Television is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors.

Chrominance (C)
Is the signal used in video systems to convey the color information of the picture.

CMOS
“Complementary Metal–Oxide–Semiconductor: is a light sensitive chip used to record image information. A CMOS sensors consists of more electronic parts than a CCD which results in less sensitivty compared to a CCD. Not as popular as CCD chips yet, but quality is improving rapidly and its advantages - lower production costst and power consumption - are many. CMOS can use either “rolling” or “global” shutter”

C-mount
Type of lens mount. C-mount lenses provide a male thread which mates with a female thread on the camera. The thread is nominally 1 inch (25 mm) in diameter, with 32 threads per inch. The flange focal distance is 17.526 millimetres for a C-mount

CS-mount
Type of lens-mount. has a flange focal distance of 12.52 millimetres and is otherwise identical to the C-mount. Can not be used on C-mount camera.

Component video
“is a video signal split into different components to transmit an analogue video signal (3 component)
Signal types are RGB, S-Video or YPbPr”

Composite video
Analogue video signal. Usually in standard formats such as NTSC, PAL, and SECAM. In consumer area’s it’s mostly used with a yellow RCA connector

Cropping
Removing unwanted areas from a digital image

Depth of field
“Depth of field (DOF) refers to what is and isn’t sharp in a picture. Images with great depth of field have a large zone of sharpness, so that everything from just a few feet in front of the camera to infinity will be sharp. Depth of field at a given focusing distance extends 1/3 in front of the point of focus and 2/3 behind it. The three key factors to depth of field are aperture, lens type or focal length and subject distance.“

Depth of focus
Is a lens optics concept that measures the tolerance of placement of the image plane in relation to the lens

Diaphragma
A stop in the light path of a lens, having an aperture that regulates the amount of light that passes. Common F-numbers are 0.85-1.0-1.4-2-2.8-5.6-...-16-22-...

Distortion
Is the alteration of an image

DPI
Dots Per inch: is a measure of spatial printing or video dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm). The DPI value tends to correlate with image resolution, but is related only indirectly.

DVI
stands for Digital Video Interface: it’s a digital video interface There are three types of DVI connections: DVI-Digital, DVI-Analog, and DVI-Integrated (Digital & Analog)

Dynamic range
“is the amount of detail that a sensor can record between highlights and shadows in an image. Scenes that have bright sunlight and deep shadows are said to have a high dynamic range. Some cameras let you decrease contrast in these situations to bring dynamic range within the camera’s limits. No camera and not even the human eye, can record the nearly infinite dynamic range that exists in real life”

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Filter
Dichromatic filters are used for colour separation and are based on dielectric interference. These optical filters, which are used in optical transmission technology, in displays and in projectors, work without absorption and have a high degree of light permeability and excellent colour accuracy. Their selectivity is very high and reaches approximately 80 % permeability for a change in wavelength of a few nanometres. Dichromatic filters are available as low-pass, high-pass and band-pass filters.

F-mount
The F-mount connector is used by CARL ZEISS for its SLR cameras and lenses. Since these 35 mm lenses enjoy an excellent reputation for their optical performance, it has also become common to use them in image processing in cases where the larger image areas must be exposed than is possible with C-mount lenses. Unlike the C-mount and CS-mount, the F-mount is not a threaded connector, but a bayonet connector.

Focal lenght
The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. The focal length determines how much magnification a lens provides. A shorter focal length lens will be able to see a wider angle of view on a scene. A longer focal length has a narrower angle of view on the scene, but a higher level of magnification.

FOV
Field Of View

F-stop
A numerical designation that indicates the size of the aperture. Smaller numbers like f2.8 denote a large opening while a large number such as f16 denotes a small lens opening.

Global shutter
A global shutter exposes the entire imager simultaneously. The entire frame is exposed and begins gathering light; when the predetermined “shutter speed” has elapsed, the sensor stops gathering light and turns its current exposure into an electronic image. There is no physical “shutter” that covers and uncovers the sensor; it’s all done with timing. At the start of exposure the entire sensor starts gathering light; at the end of exposure the light-gathering circuitry is turned off and the contents of the sensor are then “read out” to become an image.

GUI
Graphical User Interface.

HDMI
High Definition Multimedia Interface. Uncompressed all digital interface.

HD-SDI
High Definition - Serial Digital Interface: is used for transmission of uncompressed, unencrypted digital video signals (optionally including embedded Audio and/or Time Code) within television facilities; they can also be used for packetized data. They are designed for operation over short distances (< 300m) with coaxial cable.

Hue
Is one of the main properties of a color, defined technically as the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, blue, and yellow.

Interlaced scan
Sensors who expose and transmits half frames.

Iris
The lens “iris” is a mechanical device for controlling the lens aperture (lens opening). A lens may be fixed, manual controlled and/or voltage controlled.

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LED
Light Emitting Diode is a semiconductor light source.

Linescan camera
A camera which consists of a CCD with only a single line of light sensitive elements. Mostly with a very high resolution. Common values are 1024, 2048 or 4096 pixels

Luminance (Y)
Represents the brightness in an image (the “black and white” or achromatic portion of the image).

Minimum object distance (M.O.D.)
The closest distance a lens can focus on an object. Generally the smaller the focal length, the shorter the M.O.D. This distance can be altered with use of extension tubes.

NTSC
National Television System Committee is the analog television system used in most of the Americas and Asia. 252 Tvlines/ 60hz

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PAL
Phase Alternating Line: is an analogue television encoding system used in broadcast television systems in large parts of the world (625 lines/25 Frames per second). Other common analogue television standards are NTSC and SECAM.

Progressive scan
Sensors who transmit the entire image in one piece.

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Resolution
“the overall size of a digital image is measured in pixels. They are grouped in a matrix of coloured dots. The density of this matrix determines the amount of detail the image can show. This is known as resolution. Pixel dimensions for digicams may range from 2400 x 1800 or higher to resolutions as low as 800 x 600 or even 640 x 480.“

RGB
Red, Green and Blue - the primary colors from which all colors are derived. They form the additive color system, when combined in equal quantities they form white.

Rolling shutter
A rolling shutter exposes different portions of the frame at different points in time, “rolling” through the frame. It’s not an actual physical moving shutter that’s doing this (as opposed to a movie camera, which actually has a moving physical shutter). Instead, the sensor is telling different portions to become light-sensitive at different moments in time, and as this process proceeds down the course of the full frame, until the entire frame is exposed.

Shutter
the mechanical shutter of a traditional camera for taking photographs.

SLR
Single Lens Reflex camera – The camera’s lens is used for composing the frame and capturing the image to memory. A mirror system lets you view the image through the lens.

Smear
Smear is a effect created by imperfection of CCD sensor. Every video camera have a CCD sensor, due to imperfect of the CCD sensor, strong light enter CCD sensor will penetrate the photo resistance layer and create fag image. These unwanted image is called smear. the extend of a CCD camera can reject strong light is called Smear Rejection Ratio.

SNR
The SNR of an image is usually defined as the ratio of the mean pixel value to the standard deviation of the pixel values.

Spectral sensitivity
CCD sensors do not react to light of different wavelengths in the same way as the human eye. The spectral range of a CCD is much broader of the human eye ans starts from wavelenghts of 200nm up to 1100nm whereas the human eye only respons to wavelengths between 400nm and 700nm.

S-video
Separate video, also called Y/C. Is an analog video signal that carries video data as two separate signals: luma (luminance) and chroma (color).

Telecentric lens
is a compound lens which has its entrance or exit pupil at infinity. This means that the chief rays (oblique rays which pass through the center of the aperture stop) are parallel to the optical axis in front of or behind the system, respectively.

Time of Flight (TOF) camera
Is a camera system that creates distance data with help of the time-of-flight (TOF) principle. The simplest version of a time-of-flight camera uses light pulses. The illumination is switched on for a very short time, the resulting light pulse illuminates the scene and is reflected by the objects. The camera lens gathers the reflected light and images it onto the sensor plane. Depending on the distance, the incoming light experiences a delay.

UV lens
A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz or some other material transparent to ultraviolet radiation, as glass is opaque in that region.

VBS
Video, Blank, and Sync signal (composite).

VGA
Video Graphics Array, 640×480 pixels.

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Y/C signal
See S-video.

YUV
“The Y component determines the brightness of the color (referred to as luminance or luma), while the U and V components determine the color itself (the chroma). Y ranges from 0 to 1 (or 0 to 255 in digital formats), while U and V range from -0.5 to 0.5 (or -128 to 127 in signed digital form, or 0 to 255 in unsigned form). Some standards further limit the ranges so the out-of-bounds values indicate special information like synchronization.cOne neat aspect of YUV is that you can throw out the U and V components and get a grey-scale image. Since the human eye is more responsive to brightness than it is to color, many lossy image compression formats throw away half or more of the samples in the chroma channels to reduce the amount of data to deal with, without severely destroying the image quality.“

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